1. Technical Field
The present invention relates to an information processing apparatus, and particularly to reduction in electrical power consumed to operate the information processing apparatus.
2. Description of Related Art
A process of reducing electrical power consumed to operate an information processing apparatus is known. As the process, changing an operation clock of each device equipped in an apparatus, changing an operation voltage, changing display brightness, and stopping power supply, etc. are exemplified. Such processes are especially important in an apparatus such as a cellular phone and a portable computer which is operated by an electrical power supplied by a battery. The device include, for example, a main storage unit, an external storage medium connecting unit, an external storage medium, a display such as LCD, a backlight of a display or an input device configured by a plurality of keys, a communication unit, a camera, an image and/or voice processing unit for performing encoding or decoding, a voice amplifying unit, and a CPU. Each of the devices performs a process of reducing power consumption integrally or individually.
The reduction in the power consumption enables a battery to be used longer until battery charge or battery exchange.
When an amount of electrical power stored in a battery is less than a predetermined threshold value, the process of reducing the power consumption is performed or a process of further reducing power consumption is performed.
However, when an operation is restored to a normal operation during use of the device in which the process of reducing the power consumption is performed, the device cannot be immediately used or the performance thereof cannot be immediately restored. Consequently, response of the apparatus may be inconvenient for a user. Moreover, since the electrical power consumed in an operation for restoration is not an electrical power used in a normal operation, the consumed electrical power may be wasteful. As a result, in such a circumstance, determination whether to perform reduction in the power consumption is important.
In a case where a device of the apparatus is not used, it is effective not to supply electrical power to the device in terms of reduction in the power consumption, but the above-described may occur. For example, in order to access to an external storage medium in which power supply is being stopped, a process of reading information inherent to the medium stored in the external storage medium and an authentication process require time. Moreover, if the external storage medium is a disc such as an HDD, a CD, or a DVD, it is necessary to have a predetermined time until re-rotation of the disc medium at a predetermined speed.
JP-A-2006-164203 teaches a process of suppressing deterioration of the response of the apparatus and reducing the power consumption by storing the information stored in the disc medium to a storage unit of the apparatus before reduction in the power consumption, and operating the apparatus on the basis of the information stored in the storage unit of the apparatus as much as possible.
However, a method disclosed in JP-A-2006-164203 does not give a solution to the user operability since the response of the apparatus deteriorates if the information stored in the storage unit of the apparatus cannot operate the apparatus. For example, suppose that the storage medium is an SD card and the authentication process is necessary before the operation of the storage medium, a problem may also arise in that the reduction in the time for the authentication process is not possible.